While it is not known to evolve into or from any other Pokémon, it does have two different appearances: Red-Striped, one has a red stripe and irises, with a round eye and spiky fins; Blue-Striped, the other has a blue stripe and irises, with a slit eye and smooth fins.

Biology

Physiology

Basculin has the look of a typical fish, with its bottom part being green and its top part being black, the two parts being separated by a bright red or blue stripe, the rarity of each depending on which game it is encountered in. Red-Striped Basculin has a round eye and spiky fins, while Blue-Striped Basculin has a thin eye and smooth fins. They both have a spiky dorsal fin and a big jaw.

Gender differences

None.

Special abilities

Behavior

Basculin are violent in nature, and they have a particular dislike for differently colored Basculin. They often form schools of the same color. Red and blue Basculin tend to fight each other immediately upon meeting. Occasionally, opposite colors of these Pokémon will get mixed into the other's school.

Trivia

In Black and White, Blue-Striped Basculin have the same two standard possible Abilities as Red-Striped Basculin—Reckless and Adaptability (and is listed as such in Pokédex 3D); however, the Blue-Striped Basculin that can be obtained via in-game trade in White has the Ability Rock Head. In Black 2 and White 2, Blue-Striped Basculin's two standard possible Abilities are Rock Head and Adaptability, while Red-Striped Basculin's stay the same (and are listed as such in Pokédex 3D Pro).

This indicates that Blue-Striped Basculin may have been intended to have Rock Head instead of Reckless in Black and White, but resulted in having the same Ability as Red-Striped Basculin due to an oversight.

This makes Blue-Striped Basculin the only form of a Pokémon that can legitimately have one of four different Abilities.

Basculin shares its species name with Zweilous. They are both known as Hostile Pokémon.

Basculin's Pokédex entry in Pokémon Black 2 and White 2 describe the species as being very tasty, one of the rare instances that hint at Pokémon being used for food.

Origin

Basculin were most likely inspired by betta fish. Both sexes of betta display horizontal bars of color either when frightened or setting up a pecking order. They are very violent and can even fight to the death. Its appearance may have been based on a bass or piranha, the latter of which has historically been viewed as violent.

According to interviews with Ken Sugimori in Nintendo Dream, Basculin was created late in development when they realized there were few new 'standard' fish-like Pokémon in Unova, the only others being Alomomola, Stunfisk, Frillish and Jellicent. It was given two forms to make up for the small amount of fish in the region, and based on a bass since there are wild bass in New York state.